Performance of a non-volatile semiconductor storage device which performs electron writing by hot electrons and hole erasure by hot holes is improved. A non-volatile memory cell which performs a writing operation by electrons and an erasure operation by holes has a p-type well region, isolation regions, a source region, and a drain region provided on an Si substrate. A control gate electrode is formed via a gate insulating film between the source region and the drain region. In a left-side side wall of the control gate electrode, a bottom Si oxide film, an electric charge holding film, a top Si oxide film, and a memory gate electrode are formed. The electric charge holding film is formed from an Si nitride film stoichiometrically excessively containing silicon.